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Manual page for XSTR(1)

xstr - extract strings from C programs to implement shared strings

SYNOPSIS

xstr -c filename [ -v ] [ -l array ]
xstr [ -l array ]
xstr filename [ -v ] [ -l array ]

DESCRIPTION

xstr maintains a file called strings into which strings in component parts of a large program are hashed. These strings are replaced with references to this common area. This serves to implement shared constant strings, which are most useful if they are also read-only.

The command

: xstr -c filename

extracts the strings from the C source in name, replacing string references by expressions of the form &xstr[number] for some number. An appropriate declaration of xstr is prepended to the file. The resulting C text is placed in the file x.c, to then be compiled. The strings from this file are placed in the strings data base if they are not there already. Repeated strings and strings which are suffixes of existing strings do not cause changes to the data base.

After all components of a large program have been compiled, a file declaring the common xstr space called xs.c can be created by a command of the form

: xstr

This xs.c file should then be compiled and loaded with the rest of the program. If possible, the array can be made read-only (shared) saving space and swap overhead.

xstr can also be used on a single file. A command

: xstr filename

creates files x.c and xs.c as before, without using or affecting any strings file in the same directory.

It may be useful to run xstr after the C preprocessor if any macro definitions yield strings or if there is conditional code which contains strings which may not, in fact, be needed. xstr reads from the standard input when the argument `-' is given. An appropriate command sequence for running xstr after the C preprocessor is:

cc -E name.c | xstr -c -
cc -c x.c
mv x.o name.o

xstr does not touch the file strings unless new items are added; thus make.1 can avoid remaking xs.o unless truly necessary.

OPTIONS

-c filename: Take C source text from filename.
-v: Verbose: display a progress report indicating where new or duplicate strings were found.
-l array: Specify the named array in program references to abstracted strings. The default array name is xstr.

FILES

strings: data base of strings
x.c: massaged C source
xs.c: C source for definition of array ``xstr''
/tmp/xs*: temp file when xstr filename doesn't touch strings

BUGS

If a string is a suffix of another string in the data base, but the shorter string is seen first by xstr both strings will be placed in the data base, when just placing the longer one there would do.